North Korea has threatened to nuke Japan and reduce the US 'to ashes and darkness' in response to the latest sanctions imposed by the UN.

The threat was issued via the North's state news agency as US defense officials said the regime has spent the last 48 hours moving mobile missile launchers and preparing fixed sites for launch.

Elsewhere analysts from Johns Hopkins University said Kim Jong-un's regime appears to be readying its nuclear test site for more detonations following the explosion of what North Korea claims was a hydrogen bomb on September 3.

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North Korea has threatened to reduce the US 'to ashes and darkness' and 'sink Japan' with a nuke after their latest test of what the regime claims was a hydrogen bomb at the Punggye-ri nuclear test site (pictured before the launch)

New satellite imagery shows multiple landslides around the test site caused by the explosion, and suggests part of the testing facility under the North Portal has collapsed

In a statement released by news agency KCNA, a spokesman for the regime said: 'The army and people of the DPRK are unanimously demanding that the Yankees, chief culprit in cooking up the "sanctions resolution", be beaten to death as a stick is fit for a rabid dog.

'There's limit to patience. Now is the time to annihilate the U.S. imperialist aggressors. Let's reduce the U.S. mainland into ashes and darkness.

'Let's vent our spite with mobilization of all retaliation means which have been prepared till now. These are voices of the Korean army and people.

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'Also heard in the DPRK are strong accusations against the Japs who have zealously joined in the U.S. racket for sanctions.

'The behaviors of Japs, sworn enemy of the Korean nation, are enraging us. The wicked Japs should not be pardoned...

'A telling blow should be dealt to them who have not yet come to senses after the launch of our ICBM over the Japanese archipelago.

'The four islands of the archipelago should be sunken into the sea by the nuclear bomb of Juche. Japan is no longer needed to exist near us.'

Japan's chief cabinet secretary Yoshihide Suga called the statement 'outrageous', saying it 'escalates tension in the region and is absolutely unacceptable.'

However increased activity around the South Portal suggests the regime could be preparing the site for future tests, despite the UN sanctions

Activity around the West Portal (pictured left) indicates that this could be another site used by the regime for more nuclear testing

The statement came as NBC news said three senior US defense officials had confirmed that the North had been observed moving multiple mobile missile launchers and preparing 'hard sites' for launch.

Analysts believed that North Korea's latest missile, the Hwasong-14 is capable of ranging most of the mainland US, and has already been fired over Japan.

The North claims that the nuclear warhead it tested at its Punggye-ri Nuclear Test Site on September 3 is small enough to fit on the tip of the missile, though there are doubts as to whether it has the technology to bring it back to earth intact.

The troubling developments came as new commercial satellite imagery released by Johns Hopkins University via the 38North website showed new activity at Punggye-ri.

Analysts from the US-Korea Institute at the university observed multiple large landslips at the northern end of the site, which are more extensive than those seen after previous nuclear tests.

A rectangular subsidence 'crater' at the northern end of the site, near Mount Mintap, suggests that part of the site has collapsed due to the force of the last blast.

However, increased activity around southern and western underground portals suggests new areas are now being prepared to carry out future tests.

Kim Jong-un's regime claimed the test was of a hydrogen bomb (pictured) which is much more powerful than weapons previously tested at the same site

The North also claims its new warhead is small enough to be fitted to the Hwasong-14 missile, which experts believe is capable of ranging most of the mainland United States

The threats came after the UN security council voted unanimously on Monday to impose fresh sanctions on North Korea following the nuclear test

'Imagery from September 8 shows a large tractor/trailer cargo truck in the South Portal Area for the first time, and mining carts and other equipment are present outside the West Portal,' Frank Pabian, Joseph Bermudez Jr. and Jack Liu said.

'Such activity, coming shortly after the largest underground nuclear test conducted at Punggye-ri to date (via the North Portal), suggests that onsite work could now be changing focus to further prepare those other portals for future underground nuclear testing.'

The UN Security Council voted unanimously on Monday to impose fresh sanctions on North Korea following its latest nuclear test.

Measures include the complete ban on North Korean labour being used overseas, which earns the regime an estimated $500million per year.

North Korea citizens are often forcibly transferred overseas to work, given a subsistence wage and then forced to send the rest of what they earn back to Pyongyang.

Dozens of countries are thought to make use of such labour - including future World Cup host Qatar, but it is most prominent in China and Russia.

Further measures were designed to hit North Korean coal and textile exports, oil imports and impose asset freezes on regime officials.